FastECU

Two ways to tune your Subaru

Tune, flash, and diagnose your Subaru ECU

FastECU reads, writes, and tunes Subaru ECUs and TCUs over K-Line and CAN — calibration editing, bench unbricking, and live datalogging, grown from a mature Qt/C++ desktop app into FastECU NextGen, a new cross-platform rewrite.

Download FastECU View source (Qt)

Windows & Linux today, with macOS support arriving in FastECU NextGen.

FastECU's calibration editor showing heatmap-colored fueling and ignition timing maps

FastECU's calibration editor — heatmap-colored 2D/3D maps, live tuning, multiple calibration files open at once.

Two builds, one project

Pick your FastECU

The original Qt/C++ app does the full job today. A ground-up Electron/TypeScript rewrite is catching up to it feature-by-feature, cross-platform from day one.

Qt / C++ Stable

FastECU

The original, full-featured desktop app

Years of real-world Subaru tuning: live ECU read/write over K-Line and CAN, bench unbricking (BDM & bootmode), calibration editing, and live datalogging — for Windows and Linux. Free and open source under the GPLv3.

View source →
Cross-platform In development

FastECU NextGen

The next generation, in progress

A ground-up rewrite of the same tool: multi-ROM calibration editing, RomRaider/EcuFlash definitions, and live ECU communication being rebuilt protocol-by-protocol — starting with Subaru Denso SH7058 CAN read/write.

See what's new →

FastECU (Qt)

What FastECU can do today

The full feature set of the mature, actively-used desktop app.

Live ECU communication

  • Read, test-write, and write ROMs directly over K-Line or CAN
  • Seed-key access methods per ECU/protocol
  • 17 ECU platforms and 7 TCU platforms supported — see full list below

Bench unbricking

  • BDM recovery for Denso HC16 ECUs
  • Bootmode kernel upload for early UJ/WA-series ECUs
  • Custom kernels ported from the nisprog/npkernel projects

Calibration & tuning

  • 1D/2D/3D map grid editing with heatmap-colored cells
  • Fine/coarse +/- adjustment, "set value" expressions, interpolation
  • Copy & paste between maps

Definition files

  • RomRaider and EcuFlash XML definition formats
  • Automatic downloads and updates from a shared definition server

Live datalogging

  • Basic SSM value logging with Play/Stop/Record
  • Log to file for later review

Platforms

  • Windows 7 32/64-bit and Linux, precompiled
  • Open Port 2.0 and generic OBD-cable (FTDI, CH340) adapters tested

FastECU NextGen

What's new in FastECU NextGen

Built from scratch in React/TypeScript, not a straight port — some things are new or improved, some are still catching up to the original.

Multi-ROM editing

Load and tune more than one ROM file at once — each keeps its own map cache, selection, and expanded tree state, so switching between them never loses your place.

Toggleable definition sources with parse warnings surfaced

RomRaider, EcuFlash, and your own custom definitions are independently enabled with a configurable priority "main" source. Malformed or incomplete definitions show up as warnings in-app instead of silently vanishing.

Real OS clipboard for copy/paste

Ctrl+C/Ctrl+V round-trips through an actual spreadsheet, and works across different maps — even different loaded ROMs.

Cross-platform from day one, macOS included

A new Linux/macOS J2534 transport (OpenPort 2.0 AT-command protocol) sits alongside plain serial and Windows J2534 vendor DLL support.

Always-on application logger

Independent of ECU datalogging — the app's own activity is logged to disk on a background thread, with a configurable retention count, for diagnosing FastECU itself.

Live ECU communication is being rebuilt protocol-by-protocol

Subaru Denso SH7058 (CAN) connect/read/test-write/write already works end-to-end from the toolbar. Broader protocol coverage, DTC read/clear, and live datalogging are still in progress — every protocol from the original is already wired into the vehicle picker, waiting on its read/write implementation.

FastECU (Qt)

Supported ECUs & TCUs

Flashing over OBD is supported today for the following platforms.

ECU — flashing over OBD

  • Forester, Impreza, Legacy Turbo 1999–2000 K-Line (UJ WA12212920/128KB)
  • Forester/Impreza/Legacy 16bit Denso 2001–2005 K-Line (Denso HC16/160KB)
  • Forester JDM Cross Sports (Denso SH7055/512KB)
  • Legacy JDM GT MY03+ (Denso SH7055/512KB)
  • Legacy JDM GT MY05+ (Denso SH7058/1MB)
  • Impreza WRX/STi MY06–07 (Denso SH7058/1MB)
  • Impreza WRX/STi MY08+ (Denso SH7058S/1MB)
  • Impreza, Legacy Diesel MY07+ EURO4 (Denso SH7058S/1MB)
  • Impreza, Legacy Diesel MY11+ EURO5 CAN (Denso SH7059/1536KB)
  • Forester, Impreza, Legacy 2000–2002 K-Line (UJ WA12212930/256KB)
  • Forester, Impreza, Legacy 2002–2005 K-Line (UJ/Hitachi WA12212940/384KB)
  • Forester, Impreza, Legacy 2002–2005 K-Line (UJ/Hitachi WA12212970/512KB)
  • Forester 2006, Impreza 2006–2007 K-Line (Hitachi WA12212970WWW/512KB)
  • Forester 2007–2008, Impreza 2008+, Legacy 2006+ CAN (Hitachi WA12212970WWW/512KB)
  • Forester 2009–2011/Legacy 2010–2011 CAN (Hitachi SH7058/1MB)
  • Forester, Impreza, Legacy, BRZ 2013+ CAN-bus (Denso SH72531/1.25MB)
  • Forester 2013+ CAN (Hitachi SH72543/2MB)

TCU — flashing over OBD

  • CAN (Denso SH7055/512KB)
  • CAN (Denso SH7058/1MB)
  • CVT CAN (Hitachi M32176F4/512KB)
  • K-Line (Hitachi M32176F4/512KB)
  • CAN (Hitachi M32176F4/512KB)
  • CVT CAN (Mitsubishi MH8104/512KB)
  • CVT CAN (Mitsubishi MH8111/1.5MB)

Bench flash (unbrick)

  • BDM: Forester/Impreza/Legacy 16bit Denso 2001–2005 (HC16/160KB) — ROM implemented, TPU in progress
  • Bootmode: Forester, Impreza, Legacy Turbo MY99–00 (UJ WA12212920/128KB)
  • Bootmode: Forester, Impreza, Legacy 2000–2002 K-Line (UJ WA12212920/128KB)
  • Bootmode: Forester, Impreza, Legacy 2000–2002 K-Line (UJ WA12212930/256KB)

In development / planned

  • Impreza, Legacy Diesel MY17+ EURO6 CAN (SH72543/2MB) — in development
  • Forester 2013+ CAN (Hitachi SH7059/1.5MB) — planned
  • Bootmode: 2002–2005 K-Line (UJ/Hitachi WA12212940/384KB, WA12212970/512KB) — in development

In FastECU NextGen, every one of these protocol definitions is already wired into the vehicle picker — live read/write support is being added protocol-by-protocol, starting with Subaru Denso SH7058 CAN.

Get FastECU

Two products, two ways to get them.

FastECU

Free & open source (GPLv3)

Precompiled Windows & Linux builds are coming to this page soon. In the meantime, build it yourself from source.

View source on GitHub

FastECU NextGen

Subscription access, opening soon

Details on pricing and availability are coming to this page soon.

Coming soon